I was 9 years old when this was shown, back in March 1966.
I never got scared about programmes on TV; but this changed all that. The build up was scary enough but that final scene....well, I can still picture it vividly today. The heart burning on the fire whilst the shredded curtains billowed against the open windows. I watched it through my fingers which were pressed against my face but, of course, I HAD to watch!
A follow up was done by the BBC in the early 70's which is on YouTube and is good enough but regrettably not in the same league as this one. Unfortunately this version no longer exists; so much stuff was wiped back in those days as soon as it had been broadcast so the tapes could be re-used. What sacrilege!